1. Field of the Invention
The present invention relates to a plasma apparatus, and more particularly to a plasma apparatus which improves an RF feed through installed to apply RF power to a plasma electrode.
2. Description of the Background Art
In general, the conventional plasma apparatus has a problem that an RF feed through to which RF is applied has a short life span. A Kanthal wire is generally used as the RF feed through. However, the RF feed through composed of the Kanthal wire is oxidized or phase-transformed when exposed in high temperature for a long time since the Kanthal wire is a wire type.
FIG. 1 is a schematic view to explain a plasma apparatus in accordance with the conventional art. Referring to FIG. 1, a plasma electrode 20 of stainless material is installed at an upper portion of a quartz dome 10 above a plasma chamber to cover the quartz dome 10. At this time, the plasma electrode 20 has a dome shape like the quartz dome 10 and is apart from the quartz dome 10 with a predetermined interval. A bell jar 30 is installed to cover the plasma electrode 20, and an outer upper portion of the bell jar generally has a flat shape. An RF feed through 50 of a wire type penetrates a lateral side of the bell jar 30 and is connected to the plasma electrode 20. Then, RF power passes through an RF connector 40 and the RF feed through 50 sequentially and is supplied to the plasma electrode 20.
According to the conventional plasma apparatus, when RF is applied to the RF feed through 50, a lot of heat is generated since the RF feed through 50 is a wire type. Accordingly, the RF feed through 50 is easily oxidized or phase-transformed, thereby changing an impedance of the RF feed through 50. Also, the bell jar 30 is generally provided with a bell jar heater (not shown) to heat the plasma chamber. At this time, the impedance of the RF feed through 50 is more changed by the bell jar heater. If the impedance of the RF feed through 50 is changed, the RF power applied to the plasma electrode 20 is not constant, thereby degrading a reliability of a process.
Therefore, an object of the present invention is to provide a plasma apparatus which has a constant impedance even if an RF feed through is exposed in high temperature for a long time.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a plasma apparatus comprising a plasma chamber formed as a quartz dome at an upper portion thereof and having a gas inlet and a gas outlet; a plasma electrode apart from the quartz dome with a constant interval and having a dome shape like the quartz dome to cover the quartz dome; a bell jar installed to cover the plasma electrode; and an RF feed through of a stick type installed to vertically penetrate an upper portion of the bell jar so as to be connected to a peak of a center of the plasma electrode.